Why do humans have sex? This is a question few scientists have bothered to ask, probably because the answer seems obvious: pleasure and reproduction, of course. However, research suggests that the answer is more complicated. In fact, when people are actually asked why they have sex, hundreds of unique reasons emerge. Below, we'll take a look at some of the most and least common reasons reported for having sex and consider the ways they’re similar and different across the sexes.

Let’s consider the results from a series of studies conducted by Drs. Cindy Meston and David Buss. In their first study, they recruited 444 men and women aged 17-52 from college classes and the local community in Austin, Texas. Participants were presented with the following open-ended response question: “Please list all the reasons you can think of why you, or someone you have known, has engaged in sexual intercourse in the past.”

The researchers then complied a comprehensive list of reasons, after combining reasons that were identical or very similar. In the end, they identified 237 distinct reasons for having sex!

Clearly, we aren’t just having sex because it feels good or because we want to make babies.

In their second study, 1,549 college students were given the list of 237 reasons and, for each one, they were asked to indicate approximately how many of their previous sexual experiences could be attributed to that reason on a scale ranging from 1 (none of my sexual experiences) to 5 (all of my sexual experiences).

Below are the 10 most common reasons for sex reported by women and men.

SOURCE: MESTON & BUSS (2007)

What you see in the table above is that men and women are surprisingly similar when it comes to their motivations for sex. Indeed, eight out of the top ten ranked reasons were the same. One of the major differences that emerged was that “I realized I was in love” and “I was swept up in the heat of the moment” made the women’s list, while “I wanted an orgasm” and “I wanted to please my partner” made the men’s list.

Related to this, the only other noticeable difference was that women appeared to rank reasons dealing with love and affection higher than men, whereas men ranked reasons dealing with feeling good and having fun higher than women.

Now, let’s take a look at the 10 least common reasons for sex.

SOURCE: MESTON & BUSS (2007)

Again, this table reveals that men and women are more similar than different. Seven out of the bottom ten ranked reasons were identical. I should point out that although some of the reasons listed here are pretty disturbing (e.g., “I wanted to spread a sexually transmitted disease” and “I wanted to punish myself”), all of them were very rare. The average endorsement rating for each item that appeared in the bottom ten was 1.04 or less for women and 1.12 or less for men. When you consider that 1 was the lowest possible response on the scale, it tells us that very few people are having sex for these reasons.

Men and women are clearly similar when looking at the most and least commonly reported reasons for sex. However, when considering the reasons that appeared in the middle of the list (i.e., things that only motivate people from time to time), a number of notable sex differences emerged.

The nature of these differences were such that men were more likely to (1) report sex for physical reasons (e.g., “The person was too sexy to resist”), (2) say they'd have sex because it would improve their social status (e.g., “I wanted to brag to my friends about my conquests”), and (3) say they'd do it because they simply had an opportunity for sex (e.g., “The person was available”). By contrast, women were more likely than men to report sex for reasons such as “wanting to feel feminine” or because they “realized they were in love.”

As you can see, sexual behavior is motivated by far more than just pleasure and reproduction. Humans have sex for an incredibly diverse range of reasons. Certainly, there are some important differences in what motivates men and women to get it on; however, the reasons that lead us to have sex most frequently actually appear to be quite similar across the sexes.